Inertia-tilt switch

ABSTRACT

An inertia and tilt activated switch suitable for use in an alarm system, responsive to small angular and velocity deviations and capable of discriminating against false activation due to sudden jarring, bumping, or the like. A conductive ball rests in a drum-shaped housing, the floor and roof of which are electrodes normally insulated from one another. The floor electrode is slightly concave, having radius of curvature considerably greater than the diameter of the ball or the diameter of the floor electrode. The concavity allows the ball to roll into simultaneous contact with both electrodes when the housing is sufficiently disturbed from the resting orientation, thereby completing an electrical circuit. An optional delaying mechanism suppresses output from the system until the circuit has been continuously activated for a predetermined time interval.

United States Patent [191 Byers Oct. 2, 1973 INERTIA-TILT SWITCH PrimaryExaminer-Donald J. Yusko [76] Inventor: William L. Byers, Glidden St.,Attorney-Russell Nlelds Newcastle, Maine 04553 57 ABSTRACT [22] F'led:Sept 1972 An inertia and tilt activated switch suitable for use in [21 A1 N 203,009 an alarm system, responsive to small angular and velocitydeviations and capable of discriminating against false activation due tosudden jarring, bumping, or the [52] Cl 340/262 340/52 H like. Aconductive ball rests in a drum-shaped housing, [51 Int. Cl. "01h 35/02,G08) 13/00 the floor and roof of which are electrodes normally [58]Field Search 340/224 262; sulated from one another. The floor electrodeis slightly 200/6145 61-52 concave, having radius of curvatureconsiderably greater than the diameter of the ball or the diameter of[56] Reierences cued the floor electrode. The concavity allows the ballto roll UNITED STATES PATENTS into simultaneous contact with bothelectrodes when l,9l5,267 6/1933 Bigelow zoo/61.52 the housing issufficiently disturbed from the resting 3,564,496 2/1971 Brooks etal..... ZOO/61.45 X orientation, thereby completing an electricalcircuit. 3,619,524 ll/197l Gillund 340/262 X An optional delayingmechanism suppresses output 3-646'543 2/ 1972 Morris a s 340/262 fromthe system until the circuit has been continuously 3,668,675 6/l972Joens 340/261 activated for a predetermined time interval.

6 Claims, 6 Drawing Figures Patented Oct. 2, 1973 3,763,484

I INER'llllA-TILT SWITCH BACKGROUND OF THE INVENTION The presentinvention relates to an electrical system activated by an inertia-tiltswitch and more particularly to an alarm system sensitive to slightdeviations in velocity and angular orientation but desensitized tosudden, transient stimuli of the same nature.

Tilt responsive switches and inertia switches (responsive toacceleration and deceleration) generally are known to the art and havebeen considered useful in monitoring gross deviations from a standard,stable physical conditions. For example, precursors of the presentinvention have been used as ignition cut-off switches for overturnedvehicles andas detonationinitiating means in contact sea mines. Somesuch switches have been employed in tamper-alarm systems where theactivity guarded against involves a substantial disturbance of theactivating switch or where the normal condition is one of greatstability. For example, prior tilt switches may serve to indicate theopening of a hinged lid on a jewelry box.

On the other hand, such switches have heretofore not been consideredpracticable in alarm systems, stability indicators, or servo-mechanismsrequired to be sensitive to relatively small disturbances, since thesensitive switch would tend to register false alarms caused by innocuoustransitory stimuli such as bumping, jarring, etc. An example of such asituation is a theft-alarm system for automobiles in a parking lot orstorage area. The switch must be sufficiently responsive to detectunauthorized attempts to push the vehicle, as well as to drive it away,and should also respond to efforts to remove parts from the vehicle orto tamper with the vehicle in various other ways. However, the alarmshould not be actuated by a mere casual disturbance of the vehicle, forinstance, opening and closing of the doors or hood, or minor shock tothe bumpers, tires, or body of the vehicle.

SUMMARY or THE INVENTION The present invention provides an inertia-tiltswitch which is sensitive to tilting of as little as two degrees, and tocorrespondingly slight acceleration, while at the same time having theability to discriminate against stimuli such as transient bumping orjarring.

The switch contains a drum-shaped housing whose floor and roof arevconductive electrodes. These are separated by the insulating wall of thehousing. Within the housing is a conductive ball freely disposed andable to move under gravitational and inertial influences. The floorelectrode is concave, so that when the housing is in an undisturbedhorizontal orientation, the ball rests in the center part of the floor,insulated from the roof electrode. The electrodes and the ballare of theproper shape and size that upon tilting the housing a predeterminedamount (two degrees in the belowdescribed preferred embodiment) the ballrolls into simultaneous contact with the floor and the roof electrode,thus closing an electrical circuit which activates other parts of themechanism. The curvature of the floor is quite small relative to thedimension of other components of the apparatus. Thus the switch may beactivated by a slight but prolonged disturbance, but since the ball musttravel a relatively great distance from stable to circuit-closingposition, a sudden transitory disturbance will not activate the switch.The roof electrode is also slightly curved in the same fashion as thefloor electrode, assuring that activation will occur even when thehousing is completely inverted.

The switch may also include a delaying apparatus, which suppressesoutput from the system until there has been continuous activation for apredetermined length of time (approximately one-half second in thepreferred embodiment below). This feature further enables the system toavoid responding to short-lived false stimuli which are of sufficientmagnitude to activate the switch but which should be screened asunsuitable actuator of the controlled system.

In the preferred embodiment of an automobile theft and tamper alarmsystem, the switch activates an adja cent radio transmitter. Signals arereceived by a conveniently-located, near-by apparatus, and an observeris thereby notified of the disturbance of the switch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 portrays the present inventionembodied in an automobile theft and tamper alarm system.

FIG. 2 is a sectional elevation showing the interior of the switchcasing.

FIG. 3 is a diagrammatic representation of the systematic organizationof the invention.

FIGS. 4 and 5 are views similar to FIG. 6, showing other embodiments ofthe mechanism.

FIG. 6 is a top section through line 6--6 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.

FIG. 1 shows an exterior view of the present invention together with aradio transmitter which incorporates the optional signal delay in thesame housing. The entire apparatus is mounted on the dashboard of anautomobile by means of a suitable clamping device 14, there to serve asa theft alarm mechanism. The switch 11 is enclosed in an' opaquedrum-shaped casing, and the workings of the switch are not visible fromthe outside. The switch is here seated on a radio transmitter 12although other signaling devices, such as an alarm bell, can be usedadditionally or interchangeably with the transmitter. The transmitteralso houses the delayer which serves the function of suppressing signalsfrom the activated switch for approximately one-half second from thetime of activation. The close association between the switch 111 and thetransmitter/delayer 12 advantageously allows the wires from the switchto the delaying mechanism to be hidden with the casing of thecomponents, making the entire device less susceptible to sabotage. Theswitch and transmitter are in turn attached to a gimbal mount 13, whichfacilitates leveling of the apparatus on installation.

As shown in the cross-sectional view of FIG. 2, inside the switch casing21 is a volume defined by a top diaphragm 22, a bottom diaphragm 23 andthe inner wall 28 of the casing. Freely disposed within the volume andable to move under gravitational and inertial influences is a ball 25.The top diaphragm 22 is convex downward and the bottom diaphragm 23 isconcave upward. The diaphragms are disposed in approximately a parallelmanner, but the curvature of the bottom diaphragm is somewhat greaterthan that of the top diaphragm, with the result that the two diaphragmsare separated by a lesser distance around their periphery than they areat their centers. The curvature of the diaphragms is quite tion, theoutside casing of the switch is a cylinder of di-' ameter 1 inch andheight inch. The ball is of diameter three-sixteenths inch. The top andbottom diaphragms are sections of spherical shells, the bottom diaphragmhaving radius of curvature approximately 6 inches. The perimeter of eachdiaphragm is a circle of diameter about seven-eighths inch. Thus it isclear that the diaphragm is a relatively small part of a sphericalshell, and would appear quite flat. The diaphragms are disposed with thecentral radii of curvature collinear and normal to the base of thecasing, and the diaphragms are separated by a distance of approximatelyone-fourth in. between their centers. Thus, when the ball is resting onthe bottom diaphragm, with base of the casing horizontally oriented, theball is stably situated on the center of the bottom diaphragm and isseparated from the top diaphragm by a space of about onesixteenth in.However, when the ball rolls toward the periphery of the diaphragms,under the influence of gravitational or inertial stimuli, the ball (24,shown in phantom) eventually makes contact simultaneously with bothdiaphragms as the space between the diaphragms narrows.

The ball 25 should be quite round, approximating a smooth sphere. Itshould be sufficiently hard and smooth so that rolling friction betweenthe ball and the floor diaphragm is relatively low. Additionally theball should be solid, lending substantial inertia which helps to preventfalse activation from transitory stimuli.

The surfaces of the diaphragms and the ball are composed of anelectrically conducting substance. The inventor has found thatgold-plated bronze is particularly suitable, being a good electricalconductor and at the same time highly resistant to corrosion. The wall28 is an insulator and electrically separates the diaphragms. Thus, whenthe ball is in simultaneous contact with both diaphragms, an electricalcurrent will be allowed to flow between the diaphragms if there is avoltage differential between the diaphragms. Wires 26 and 27, attachedto the top and bottom diaphragms, respectively, electrically connect theball and diaphragms to other circuit parts.

In the embodiment of FIG. 2, the ball will roll into simultaneouscontact with both diaphragms under gravitational influence brought aboutby an angular deviation of the casing of as little as 2 or 3 from thehorizontal. However, it is to be understood that the scale and curvatureof the above embodiment is illustrative and not by way of limitation,and that the above shapes and dimensions may be varied to adapt theinvention for particular uses.

An alternative embodiment provides for a plurality of balls in place ofa single ball 25. A top view is afforded in FIG. 4, showing seven balls41 disposed in stable position in the center of the bottom diaphragm 42.In this case, a displacing stimulus would cause simultaneous contactwith both diaphragms at a number of loci. In addition, the switch ismore sensitive to such stimuli because some balls are closer to theperiphery of the diaphragm than is the single ball of FIG. 2. FIG. 5 isa similar view illustrating the rest configuration of a threeballswitch. Note also that three or seven are particu larly suitable numbersof balls for use in this circular housing because of the symmetricalclose-packing arrangement thus possible. However, any number of ballsmay be employed to achieve various special purposes.

The highly diagrammatic representation of FIG. 3 shows the switchmechanism 31 (described more specifically in connection with FIG. 2)including top and bottom diaphragm/electrodes 32 and 33, respectively,conducting ball 34 in circuit closing and 35 in opencircuit position,and electrical connections 36 and 37 leading to the top and bottomdiaphragm/electrodes, respectively. Shell 38 contains the remainder ofthe electrical components of the system and in the embodimentillustrated in FIG. 1, shell 38-was referred to as thetransmitter/delayer mechanism. Possible components are electrical powersource 39, a delaying mechanism 40 (optional), and an output mechanism41, which in the instant embodiment is a radio transmitter, but mayequally suitably be an audioor visualprojector, e.g., alarm bell orlight or any suitable communicator. Where a radio transmitter isemployed, a receiver (not shown) spaced a distance from the switch andtransmitter is also employed. The function of the delayer is to suppressthe output for a predetermined time interval immediately after thecircuit is closed by the ball moving into circuit-closing position. Thusthe output device is activated only after the ball has remained incircuit-closing position for longer than the predetermined timeinterval. This serves to filter out any transitory, non-significantstimuli which have not already been eliminated by the advantageousdesign of the switch and which would otherwise result in extraneousoutput or a false alarm." The inventor has found that a delay ofone-half second serves this purpose well in the car theft alarm system.Of course, a greater or shorter time delay may be provided to serveother particular functions.

It should be understood that although the embodiment herein described ofthe present invention is of an automobile theft and tamper alarm,thepresent invention is not limited to such embodiment but may usefully beincorporated in other alarm systems or mechanisms of other typesrequiring a sensitivity to slight disorientations coupled with theability to discriminate against transitory disturbance.

I claim:

1. In an electrically governed system, a gravitationally and inertiallyactivated switch comprising a housing having a bottom conductivediaphragm,

concave upward,

a top conductive diaphragm, convex downward,

each diaphragm having substantially circular perimeter and substantiallyconstant curvature, with the curvature of the bottom diaphragm beinggreater than that of the top diaphgram,

the two diaphragms symmetrically disposed relative to one another suchthat the distance between them is greatest at the center of thediaphragms and decreases toward the periphery,

the diameters of the diaphragms and the distances separating thediaphragms all small relative to the radii of curvature of thediaphrams,

the diaphragms electrically separated from one another by an insulatingwall joining the diaphragms along their periphery,

the diaphragms and the insulating wall thereby defining a volume,

a conductive mass freely disposed within the volume,

the mass having physical characteristics such that the mass 4 is ininsulated position from the top diaphragm when the housing is inundisturbed horizontal orientation but moves into simultaneous contactwith both diaphragms when the housing is sufficiently tilted oraccelerated.

2. The switch of claim 1 wherein the conductive mass is a conductiveball having diameter smaller than the distance separating the diaphramsnear their center but larger than the distance separating the diaphragmsnear their periphery.

3. The switch of claim 1 wherein the conductive mass comprises aplurality of relatively small conductive balls.

4. The switch of claim 1 further comprising means for suppressing outputfrom the system until the mass has been in simultaneous contact withboth diaphragms for an uninterrupted time interval of predeterminedlength.

5. A theft and tamper alarm system comprising the switch of claim 4 incombination with a radio transmitter activated by the switch, a radiotransmission receiver, mounting means for the switch and transmitterincluding means for permitting the switch to be secured in level,horzontal orientation, means for disposing the switch and transmitter inrelation to a desired object such that a disturbance of the object willcause a disturbance of the switch. 6. A swtich comprising: at least oneconductive sphere and a container, including a pair of opposedconductive diaphragms, enclosing said sphere said diaphragms beingspaced apart at their centers a distance greater than the diameter ofsaid sphere, said diaphragms being spaced apart at their periphery adistance less than the diameter of said sphere, each of said diaphragmshaving slight and substantially constant curvature of the sameorientation, and that surface of each of said diaphragms which isaccessible to ball contact lying between two planes narrowly spaced.

1. In an electrically governed system, a gravitationally and inertiallyactivated switch comprising a housing having a bottom conductivediaphragm, concave upward, a top conductive diaphragm, convex downward,each diaphragm having substantially circular perimeter and substantiallyconstant curvature, with the curvature of the bottom diaphragm beinggreater than that of the top diaphgram, the two diaphragms symmetricallydisposed relative to one another such that the distance between them isgreatest at the center of the diaphragms and decreases toward theperiphery, the diameters of the diaphragms and the distances separatingthe diaphragms all small relative to the radii of curvature of thediaphrams, the diaphragms electrically separated from one another by aninsulating wall joining the diaphragms along their periphery, thediaphragms and the insulating wall thereby defining a volume, aconductive mass freely disposed within the volume, the mass havingphysical characteristics such that the mass is in insulated positionfrom the top diaphragm when the housing is in undisturbed horizontalorientation but moves into simultaneous contact with both diaphragmswhen the housing is sufficiently tilted or accelerated.
 2. The switch ofclaim 1 wherein the conductive mass is a conductive ball having diametersmaller than the distance separating the diaphrams near their center butlarger than the distance separating the diaphragms near their periphery.3. The switch of claim 1 wherein the conductive mass comprises aplurality of relatively small conductive balls.
 4. The switch of claim 1further comprising means for suppressing output from the system untilthe mass has been in simultaneous contact with both diaphragms for anuninterrupted time interval of preDetermined length.
 5. A theft andtamper alarm system comprising the switch of claim 4 in combination witha radio transmitter activated by the switch, a radio transmissionreceiver, mounting means for the switch and transmitter including meansfor permitting the switch to be secured in level, horzontal orientation,means for disposing the switch and transmitter in relation to a desiredobject such that a disturbance of the object will cause a disturbance ofthe switch.
 6. A swtich comprising: at least one conductive sphere and acontainer, including a pair of opposed conductive diaphragms, enclosingsaid sphere said diaphragms being spaced apart at their centers adistance greater than the diameter of said sphere, said diaphragms beingspaced apart at their periphery a distance less than the diameter ofsaid sphere, each of said diaphragms having slight and substantiallyconstant curvature of the same orientation, and that surface of each ofsaid diaphragms which is accessible to ball contact lying between twoplanes narrowly spaced.